1. Field of the Invention
This invention relates to improvements in an engine control apparatus for an engine with a turbocharger.
2. Description of Background Art
A technique of providing a turbocharger to an engine to raise the output power of the engine significantly is well known in the art. However, the technique has a drawback that, upon acceleration of the engine, inevitably there is a lag (turbo lag) in the increase in speed of the turbocharger. Thus, the timing of supplying the supercharged air lags.
One known countermeasure against this is the xe2x80x9cControl Apparatus for Engine with Turbochargerxe2x80x9d described in the official gazette of Japanese Patent Laid-open No. Hei 5-321804. According to this technique, in order to cause a turbocharger to operate as quickly as possible upon acceleration of the engine, rich air fuel mixture is supplied into and burned in an exhaust pipe (exhaust manifold). This increases the exhaust gas pressure, and the speed of rotation of an exhaust turbine is raised with the higher exhaust gas pressure in order to obtain a higher supercharged air pressure.
According to the technique described above, upon acceleration of an engine, a required supercharged air pressure can be supplied to an intake system, and the responsiveness of the engine can be further increased.
However, since the technique is based upon combustion in an exhaust pipe, the temperature of the exhaust pipe becomes high, and damage to the exhaust pipe can become significant. Further, there is the possibility that the emission may be deteriorated.
Therefore, it is an object of the present invention to provide a technique that can improve the responsiveness of the engine upon acceleration, while at the same time extend the life of an exhaust pipe and maintain good emissions.
In order to attain the object described above, a first aspect of the present invention is based upon an ignition control apparatus for an engine with a turbocharger which includes an ignition timing control section for adjusting an ignition timing and a turbocharger, wherein the ignition timing control section carries out control of changing over the ignition timing which has been an ordinary ignition timing to a corrected ignition timing advanced with respect to the ordinary ignition timing on a condition that a throttle valve which has been in a closed state has opened rapidly.
In the engine with a turbocharger, immediately after the throttle valve opens rapidly, the supercharged air pressure is low when compared with that in an ordinary operation state, and therefore, the knocking toughness is high. Therefore, when the throttle valve is opened rapidly, the ignition timing is advanced with respect to the ordinary ignition timing. Consequently, the start of combustion is advanced, and increase of the output power of the engine and generation of exhaust gas can be urged to increase the speed of an exhaust turbine, and thus to increase engine output performance and driving performance. While combustion in an exhaust pipe is used conventionally, the present invention only requires ordinary combustion in a combustion chamber. Therefore, there is no possibility that the temperature of the exhaust pipe may rise abnormally. Thus, the life of the exhaust pipe can be extended, and the emission can be well maintained.
According to a second aspect of the present invention, the ordinary ignition timing is set to an upper limit value or a value proximate to the upper limit value on a condition that the throttle valve is not opened rapidly and knocking does not occur.
Where also the ordinary ignition timing is set to the upper limit value or a value proximate to the upper limit value, that is, advanced to the utmost, the start of combustion can be advanced and generation of exhaust gas can be urged to advance a rise of the exhaust gas turbine and urge increase of the supercharged air pressure.
According to a third aspect of the present invention, the ignition timing control section starts integration of an amount of rotation of the engine at a point of time at which the ignition timing is changed over to the corrected ignition timing. Conversely, the ignition timing control section carries out control of returning the ignition timing to the ordinary ignition timing after a point of time at which the integrated amount of rotation reaches a predetermined value.
If a fixed interval of time elapses, then the speed of rotation of the exhaust turbine rises sufficiently and a high supercharged air pressure is obtained. Therefore, at a point of time when the integrated amount of rotation reaches the predetermined value, the ignition timing is returned from the corrected ignition timing to the ordinary ignition timing. Excessive advancement gives rise to knocking. In this regard, according to the present invention, good operation of the engine can be continued while preventing knocking.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.